In the spring of 1932, somewhere out on the rolling plain of scrub oak in what grew up to be the Manuel F. Correllus State Forest, an aging male bird met an unknown but assuredly violent end. With the death of the last heath hen on Martha's Vineyard, a whole race of prairie grouse to which it had belonged vanished from the face of the earth.

It was a particularly dramatic extinction event: A bird that once ranged up and down the coastline from Maine to North Carolina had, within the space of a single generation, been extirpated from the whole of the eastern seaboard, except Martha's Vineyard. From 1870 onward, the last population of heath hens found itself cornered and isolated on what was then Great Plain and is now the state forest. Despite efforts to save its habitat and protect the flock, the heath hen fell victim to inbreeding, predation and disease, dwindling away to a single bird in 1928. The story of this last cock was followed all across the country until 1933, when it failed to appear on its old mating ground in West Tisbury and was pronounced dead by its most studious observer, Dr. Alfred Gross of Bowdoin College. It was the first time in ornithological history that an extinction was observed in the wild down to the last individual.

Now a genetic study of the skins of scores of heath hens, all of them from the Vineyard, shows that the Island bird, although it looked and behaved much like its supposed parent species in the Midwest, was a wholly distinctive creature. Genetically it was more different from the greater western prairie chicken - that supposed parent species - than the Midwestern bird is from any other family member in its genus, which includes the lesser prairie chicken, the endangered Attwater's prairie chicken of eastern Texas, and even the sharp-tailed grouse. It is possible that instead of being a subspecies of the prairie chicken - which scientists have considered it to be since it was first typed in the last years of the nineteenth century - the heath hen might have been a species unto itself.

"It gets at the question of what really is a heath hen," says Eric Palkovacs, a doctoral student in the department of ecology and evolutionary biology at Yale. Mr. Palkovacs is the lead scientist whose paper on heath hen genetics appears this month in Molecular Ecology magazine. "Is the heath hen any prairie chicken that occurred along from perhaps Maine to North Carolina, including Martha's Vineyard, before Europeans extirpated them? Or is a heath hen that population that was on Martha's Vineyard from about 1870, when the mainland population went extinct, to 1932, when the last individual died?"

These questions bear on an idea that the Vineyard conservation movement has debated, on and off, for five years at least: whether greater western prairie chickens might someday be introduced into a scrubby habitat in what is now the state forest to see if an ecological equivalent of the heath hen can, with careful management, make it on the Vineyard once again. In addition to capturing the public imagination about why ecologists use clearing and fire to restore native habitats that depend on both techniques for their vitality, the prairie chicken, argue proponents, might serve decades from now as an "umbrella species" whose fate would indicate whether the habitat on which it lived was once again in health and balance.

"Prairie chickens require vast open areas," says Tom Chase, eastern Massachusetts programs director of The Nature Conservancy, whose office is in Lambert's Cove. "Many of our other rare species, such as short-eared owls, harriers, a number of moths that feed on scrub oak, also require vast open areas. As do a number of plants. As do their pollinators. So if you're able to provide enough of a habitat that's healthy enough to keep prairie chickens alive - or their counterpart, heath hens - then it's also likely that you'll be providing more habitat, and the right kind of habitat, for all these other species."

Others dispute the notion that the prairie chicken, which lives in grassland prairie in the Midwest, could serve this purpose on a restored and scrubby Great Plain. They say that the findings in Mr. Palkovacs's study help to prove it.

"Talking about introducing a species that had never been here to influence habitat management is a nonstarter for me," says Lloyd Raleigh, regional ecologist for The Trustees of Reservations. "Just to begin with, seeing that the prairie chicken is in trouble in a lot of its range, that's where the focus should be, as opposed to a part of the range where it's never been." He calls it a foreign bird to Martha's Vineyard "in genetic terms, in behavioral terms, their choice of habitat, the amount of feathers they have. Things like that. So it's completely different."

Advocates and critics agree that the state forest, planted on the old heath hen reservation as the bird was dying out, is in need of cutting and burning to revive and restore a native habitat unique in all of New England. The Great Plain was a landscape scoured by fire from the time of the first inhabitants, studies show, and what is now the state forest contains a more densely concentrated group of state-listed plants, animals and insects than any other place in the commonwealth. Most depend on a regime of controlled burns to live, ecologists agree.

A supporter of the restoration of the processes of cutting and controlled burning in the old Great Plain habitat, Mr. Chase says that whether or not the greater western prairie chicken is ever introduced to the Island, the Vineyard must begin to embrace even greater goals, including the stitching together of fragmented habitat, reclaiming through the marketplace lands lost to development, and figuring out material ways to support a middle class that will be able to live on the Island over the long term and feel personally invested in its ecological fate.